Procedure guide
How neuromodulators such as Botox soften wrinkles, how long they last, and what the risks are.
Written by Orr Shauly, MD, plastic surgery resident. Updated .
For information and education only, not medical advice.
The short answer.
Neuromodulators are purified botulinum toxin injected in tiny doses to relax specific facial muscles, which softens the dynamic wrinkles those muscles create, such as frown lines, forehead lines and crow's feet.1,2 In placebo-controlled trials they are highly effective, and the effect begins within a few days, peaks at about 2 weeks and lasts about 3 - 4 months.1-3 Side effects are usually mild, such as bruising or headache, and drooping of the eyelid or brow is the most common notable complication.2,4
- 120 Days
- median duration
- Median duration of effect for frown lines among responders to 20 units of onabotulinumtoxinA in pooled phase 3 trials.5
- 9,669 Patients
- safety meta-analysis
- Patients in 32 randomized trials of cosmetic botulinum toxin, with an acceptable safety profile.4
- 0.5%
- antibody formation
- Patients who developed neutralizing antibodies after onabotulinumtoxinA across 33 trials and 10 indications.6
- 2 Weeks
- to full effect
- Time for the effect to plateau after injection, when results are usually assessed.2
What neuromodulators are.
Botulinum toxin blocks the release of acetylcholine at the junction between nerve and muscle, which temporarily weakens the injected muscle.1,2 Because many facial lines form where muscles repeatedly fold the skin, relaxing those muscles softens the lines.1
Several type A products are available, including onabotulinumtoxinA (Botox), abobotulinumtoxinA (Dysport), incobotulinumtoxinA (Xeomin) and prabotulinumtoxinA, with newer formulations such as daxibotulinumtoxinA.1,7 Their units are not interchangeable, so doses for one product cannot be applied to another.1
Neuromodulators improve lines that appear with movement. Deep lines present at rest often soften but are rarely erased, and they may need fillers, resurfacing or surgery.2
What neuromodulators are used for.
| Area | Target | Evidence |
|---|---|---|
| Frown Lines3,7 | Corrugator and procerus muscles between the brows | Far more effective than placebo in randomized trials of 1,474 patients |
| Crow's Feet1 | Orbicularis oculi at the outer corners of the eyes | Typically treated with injections at three sites on each side |
| Forehead Lines1 | Frontalis muscle | Usually treated together with frown lines to avoid a lowered brow |
| Neck Bands8 | Platysma muscle | Higher satisfaction than placebo in randomized trials of 912 patients |
| Jaw Contouring9 | Masseter muscle | Reduced muscle thickness and prominence vs placebo in 5 trials |
| Underarm Sweating10 | Sweat glands in the skin | Sweat production fell from 192 to 24 mg per minute in a randomized trial |
Treatment is individualized. Men and people with stronger muscles or thicker skin generally need more product, and some patients prefer a softer, more natural result while others want near-complete relaxation.2 Complete paralysis is usually avoided in favor of shaping and softening.2
Research has also found that frown line injections improve depression scores. In a meta-analysis of 9 prospective studies, depression scores fell by an average of 8.39 points at 6 weeks across 5 randomized trials, although this is not an established psychiatric treatment.11
Who is a candidate.
Candidates are adults bothered by lines that form with expression. The assessment looks at lines at rest and in motion, brow position and symmetry and any existing drooping of the eyelid or brow, which can worsen with treatment.2
Treatment is avoided with infection at the injection site or allergy to any ingredient, including albumin. It is used cautiously in people with neuromuscular disorders such as myasthenia gravis and with certain antibiotics that enhance the effect, and it is used with caution in pregnancy and breastfeeding because safety data are limited.1,2
How a treatment works.
- Assessment: Lines are photographed at rest and with expression to plan injection points.2
- Dosing: Doses are standardized for each area and product. For onabotulinumtoxinA, 20 units in five points is the standard dose for frown lines.1,3
- Injection: Fine needle injections are placed into the target muscles, avoiding nearby muscles such as the one that lifts the eyelid.1
- Aftercare: Patients are usually asked not to massage the area and to briefly limit strenuous activity, which may reduce bruising and swelling.2
- Follow-Up: Results are assessed at about 2 weeks, when touch-ups can be done.2
What to expect afterward.
| Time | What Usually Happens |
|---|---|
| Same Day2 | Minor bruising or tenderness at injection points is possible |
| Days 2 - 41,2 | The effect begins |
| Week 22 | The effect plateaus, and results are assessed |
| Months 3 - 41,5 | Muscle movement gradually returns, with a median of 120 days for frown lines in pooled trials |
| Months 3 - 62 | Treatment is typically repeated |
Side effects and safety.
| Side Effect | Reported Rate | Context |
|---|---|---|
| Any Side Effect12 | 16% | Pooled across 17,352 injection sessions |
| Bruising12 | 5% | Usually small and temporary |
| Eyelid Drooping1,2 | About 3% - 5% | Temporary, most often after frown line treatment |
| Headache1,12 | 3% - 9% | Higher in forehead line studies |
| Facial Weakness12 | 2% | Unwanted weakness of a nearby muscle, temporary |
In a meta-analysis of 32 randomized trials and 9,669 patients, treatment-related side effects were about 1.5 times more common than with placebo injections, driven mainly by eyelid or brow malposition and headache, while bruising and injection site reactions were similar.4 Another meta-analysis of 20 trials confirmed a low but real excess of side effects compared with placebo.13
Spread of the toxin effect beyond the injection site can cause swallowing, breathing or vision problems, but it is described mainly with higher medical doses and is unlikely at labeled cosmetic doses.1 Resistance from neutralizing antibodies is rare. Across 33 trials, 0.5% of patients developed antibodies after onabotulinumtoxinA, and few lost their response.6
Results and how long they last.
In pooled phase 3 trials, 84.2% of patients treated with 20 units for frown lines responded at day 30, and the median duration of effect among responders was 120 days with the brows furrowed.5 Satisfaction increased with longer duration of effect.5
Repeated treatment remains effective over time. In 50 patients treated for an average of 15 years, there was no evidence of treatment failure or shorter duration, and 94% felt they looked at least 2 years younger than their age.14 Formulations differ somewhat. In a network meta-analysis, all type A products were far superior to placebo, with daxibotulinumtoxinA ranking highest for improvement.7
Alternatives.
What we don't know yet.
- Product Comparisons: Few trials compare products directly at equivalent doses.7
- Off-Label Areas: Uses outside the established areas have less randomized evidence.1,9
- Mood Effects: How frown line treatment improves depression scores, and for whom, is not yet clear.11
- Side Effect Reporting: Registry data may underestimate side effects compared with clinical studies.12
Common questions.
How long does Botox last?
The effect usually lasts about 3 - 4 months. In pooled trials for frown lines, the median duration among responders was 120 days, and treatment is typically repeated every 3 - 6 months.
How long does it take for Botox to work?
The effect begins within about 2 - 4 days and reaches its peak at about 2 weeks, when results are assessed.
Is Botox safe?
In randomized trials of thousands of patients, side effects were usually mild and temporary, such as bruising, headache or a temporarily drooping eyelid or brow. Serious spread of the toxin is unlikely at cosmetic doses.
What is the difference between Botox and filler?
Neuromodulators relax muscles to soften lines that form with movement. Fillers add volume to fill lines present at rest or restore lost volume. The two are often combined.
Can you become resistant to Botox?
It is rare. Across 33 trials, 0.5% of patients developed neutralizing antibodies, and very few lost their response to treatment.
Does Botox prevent wrinkles?
Neuromodulators soften lines caused by muscle movement while the effect lasts, and long-term users in one study reported looking younger than their age, but strong comparative studies of prevention are limited.
Can I get Botox while pregnant or breastfeeding?
Textbooks advise caution during pregnancy and breastfeeding because there is not enough safety data, so timing should be discussed with your physician.
Are neuromodulators right for me?
Only an in-person evaluation can answer that. This guide is educational and cannot assess an individual case. A qualified plastic surgeon or dermatologist can review your goals, anatomy and health history with you.
Key terms.
- Neuromodulator
- An injectable medication, such as botulinum toxin, that temporarily relaxes a targeted muscle.
- Botulinum Toxin
- A purified protein that blocks nerve signals to muscle, used in tiny doses to soften wrinkles.
- Dynamic Wrinkles
- Lines that appear with facial expression and soften when the face is at rest.
- Static Wrinkles
- Lines visible even when the face is at rest.
- Glabellar Lines
- Frown lines between the eyebrows, formed by the corrugator and procerus muscles.
- Lateral Canthal Lines
- Crow's feet at the outer corners of the eyes, formed by the orbicularis oculi muscle.
- Neutralizing Antibodies
- Antibodies that can block the effect of botulinum toxin and cause a loss of response.
- Masseter Muscle
- The chewing muscle at the angle of the jaw, sometimes treated to slim the lower face.
- Hyperhidrosis
- Excessive sweating beyond what is needed to regulate body temperature.
References.
- 1.Hollenbeck ST, Brown DA. Botulinum toxin. In: Chung KC, editor. Grabb and Smith's plastic surgery. 8th ed. Philadelphia: Wolters Kluwer; 2020. p. 481-7.
- 2.Lemmon J, Ramanadham SR, Graivier M. Botulinum toxin. In: Janis JE, editor. Essentials of aesthetic surgery. New York: Thieme; 2018. p. 269-79.
- 3.Guo Y, Lu Y, Liu T, Zhou Y, Yang P, Zhu J, et al. Efficacy and Safety of Botulinum Toxin Type A in the Treatment of Glabellar Lines: A Meta-Analysis of Randomized, Placebo-Controlled, Double-Blind Trials. Plast Reconstr Surg. 2015;136(3):310e-318e. PubMed
- 4.Gostimir M, Liou V, Yoon MK. Safety of Botulinum Toxin A Injections for Facial Rejuvenation: A Meta-Analysis of 9,669 Patients. Ophthalmic Plast Reconstr Surg. 2023;39(1):13-25. PubMed
- 5.Glogau R, Kane M, Beddingfield F, Somogyi C, Lei X, Caulkins C, et al. OnabotulinumtoxinA: a meta-analysis of duration of effect in the treatment of glabellar lines. Dermatol Surg. 2012;38(11):1794-803. PubMed
- 6.Jankovic J, Carruthers J, Naumann M, Ogilvie P, Boodhoo T, Attar M, et al. Neutralizing Antibody Formation with OnabotulinumtoxinA (BOTOX®) Treatment from Global Registration Studies across Multiple Indications: A Meta-Analysis. Toxins (Basel). 2023;15(5):342. PubMed
- 7.Li X, Sui C, Xia X, Chen X. Efficacy and Safety of Botulinum Toxin Type A for Treatment of Glabellar Lines: A Network Meta-Analysis of Randomized Controlled Trials. Aesthetic Plast Surg. 2023;47(1):365-77. PubMed
- 8.Syed R, Khan AA, Shah S, Khan A, Idrees M, Ali M, et al. Efficacy and Safety of OnabotulinumtoxinA for the Treatment of Platysma Prominence: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Cosmet Dermatol. 2026;25(2):e70701. PubMed
- 9.Machado GF, De Freitas LR, Ribeiro LFS, Andrade GRO, Silva VP, da Silva TVD, et al. Efficacy of botulinum toxin for masseter muscle hypertrophy: A systematic review and meta-analysis. J Plast Reconstr Aesthet Surg. 2026;119:212-25. PubMed
- 10.Heckmann M, Ceballos-Baumann AO, Plewig G. Botulinum toxin A for axillary hyperhidrosis (excessive sweating). N Engl J Med. 2001;344(7):488-93. PubMed
- 11.Crowley JS, Silverstein ML, Reghunathan M, Gosman AA. Glabellar Botulinum Toxin Injection Improves Depression Scores: A Systematic Review and Meta-Analysis. Plast Reconstr Surg. 2022;150(1):211e-220e. PubMed
- 12.Zargaran D, Zoller FE, Zargaran A, Mosahebi A. Complications of facial cosmetic botulinum toxin A injection: analysis of the UK Medicines & Healthcare Products Regulatory Agency registry and literature review. J Plast Reconstr Aesthet Surg. 2022;75(1):392-401. PubMed
- 13.Zhang W, Wen Y, Zhong Y, Chen Q. Meta-Analysis of Adverse Reactions of Botulinum Toxin A in Facial Rejuvenation Treatment. Aesthetic Plast Surg. 2025;49(9):2305-14. PubMed
- 14.Trindade de Almeida AR, Martins da Costa Marques ER, Contin LA, Trindade de Almeida C, Miot HA. Long-Term Consecutive OnabotulinumtoxinA Injections for Facial Aesthetic Treatment: A Real-World Study. Dermatol Surg. 2025;51(12):1133-8. PubMed